Creative Techniques: Primer On Primers
As artists we need to be concerned with the nature of the surface to be painted. For instance, if the surface is already painted, you need to consider the physical condition of the paint as surface adhesion could become problematic. Most artists are not aware that it is critical to wash any painted surface, even a newly painted surface, with soap and water prior to application of acrylic products. Previously painted high gloss surfaces can be cleaned and dulled in one step by using a household abrasive cleaner and then washing it off thoroughly with clean water.
Once your surface or support is clean you need to prime your support. So what is a primer? A primer is a coating that is put on a support to prepare it for the acceptance of paint. Depending on which surface you are planning to work on, you will need to prime it differently. For example, it is possible to paint acrylic on to metal. Before applying the primer(s) you need to scuff or abrade the surface with fine sandpaper for the best possible adhesion. After sanding, wipe the surface with rubbing alcohol (isopropyl). This will remove any oils and contaminants that may compromise adhesion. After this is done, it is a good idea to avoid handling the surface with your bare hands as there are oils in your skin.
Primers such as XIM’s UMA (Urethane Modified Acrylic), which comes in white and clear, or an Alkyd Metal Primer are the best “transition or bridge” between metal and acrylic paints. Lightly sand the UMA to prepare it for the acrylics. Most Alkyd primers are made with proper tooth and sanding isn’t mandatory. Acrylics in general will have good adhesion to these primers. If you want to increase it further, add GAC 200 (up to 75%) to the paint. GAC 200 is a specialty acrylic polymer medium. It is very hard and promotes adhesion to non-porous surfaces. Final varnish will help protect the paint from weathering.
Example of primers or acrylic products that may be used as primers in the Golden line of products are: Acrylic Gesso, GAC 400, Absorbent Ground, Acrylic Ground for Pastels, High Loads, Acrylic Mediums and Gels (such as Fluid Matte Medium, GAC 100), Clear Granular Gel, Garnet Gel, Molding and Light Molding Paste, and Pumice Gel.
The proper sizing and priming of your canvas for an oil painting application is vital. First, what is a size or sizing? A size is a dilute solution of material applied to a porous support that prevents the absorption of paints. Thus, oil painters usually size their canvasses with a hide glue (such as rabbit-skin) to both stiffen and protect the support from the more acidic oils. Golden does make a particular additive named GAC 400, which stiffens fabric. A minimum of two coats are needed. In testing, 4 coats of Gesso were required to see similar results. In a pinch, GAC 700 (harder film surface) and Fluid Matte Medium also offered some protection. The best way to both stiffen and block oil penetration is as follows: first, apply one coat of GAC400 to the front of the canvas (for stiffening) followed by one coat of GAC100 (to block oils). Allow sufficient drying time(one to three days) to help the size coalesce.Then, apply two coats of Gesso to the front of your support.
The most commonly used primer is Acrylic Gesso. Gesso is designed to be porous and somewhat absorbent. Like any other primer, it is there to facilitate adhesion of the paint layers. Acrylic Gesso is an excellent primer for canvas and wood. The difference in price between different gessos often has to do with it’s quality. Student grade gessos, for instance, may contain low acrylic levels and high solid and water levels which may result in cracking when it is rolled, flexed or applied thickly. However, it would have good absorbency. When looking at Gessos you want one which will provide you with a good level of absorbency, opacity, and flexibility. If you want to lessen the chance of cracking when flexed on rigid supports, such as wood panels, Golden does make a Sandable Hard Gesso which contains solids that allow for the act of sanding.
Acrylic Gesso cam be used with any media, from acrylics to tempera, to alkyds and oil paints. There are no ASTM standards applied to Gesso so the general rule is you get what you pay for. If you do decide to thin down an entire bottle of thick gesso it is best to use purified or distilled water so as not to infect the Gesso with bacteria emanating from tap water. You should not dilute your Gesso more than 25 to 30%. Golden also sells a black gesso which contains a Mars Black and a Carbon Black pigment not Matting Agents. Swirls of white or grey in a Gesso indicates a cheaper Gesso. The streaks are caused by matting agents.
At times, painters may use Titanium White as a Gesso or a less costly latex paint. This is always a risky proposition. Titanium White is not absorbent enough to saturate the support and latex paints are usually not made to last more than a few years.
A quality Gesso should have a bit of “toothiness” to it. This toothiness is achieved by the addition of calcium carbonate (a non-pigment solid). If you wish to change the toothiness of your Gesso you can do so by the addition of Fluid Matte Medium or some Soft Gel Matte.
If you want to show off the natural look of your canvas or wood piece, you may want to try some Fluid Matte Medium, for a matte look and surface or, GAC 100 for a glossy surface.
HIGH LOAD ACRYLICS
Golden also offers a line of products called High Load Acrylics. These are essentially colored gessos. These high load acrylic are overloaded with actual pigment instead of the normal Titanium Dioxide pigment. The pigments act as a filler rather than using matting solids. This overloaded pigment paint has excellent tooth and porosity for handling the subsequent paint layers. The High Loads impart a beautiful, velvety matte film surface. However, this film surface is extremely marable (markable) and susceptible to burnishing. The High Loads are also very sensitive to water.
Earlier on, I spoke of examples of primers or acrylic products that may be used as primers in the Golden line of products. These are, once again, Acrylic Gesso, GAC 400, High Loads, Acrylic Mediums and Gels (such as Fluid Matte Medium, GAC 100), Absorbent Ground, Acrylic Ground for Pastels, Clear Granular Gel, Garnet Gel, Molding and Light Molding Paste, and Pumice Gel.
For more information on any of these products please visit: www.goldenpaints.comBack